Your doctor will ask questions about your symptoms and do a physical exam. Your doctor may also take a sample of fluid from your joint to look for uric acid crystals. This is the best way to test for gout. Your doctor may also do a blood test to measure the amount of uric acid in your blood.
Gout is suspected when a patient reports a history of repeated attacks of painful arthritis at the base of the toes. Ankles and knees are the next most commonly involved joints in gout. Gout usually attacks one joint at a time, while other arthritis conditions, such as systemic lupus and rheumatoid arthritis, usually attack multiple joints simultaneously.
The most reliable test for gout is finding uric-acid crystals in the joint fluid obtained by joint aspiration (arthrocentesis). Arthrocentesis is a common office procedure performed under local anesthesia. Using sterile technique, fluid is withdrawn (aspirated) from the inflamed joint, using a syringe and needle. The joint fluid is then analyzed for uric-acid crystals and for infection. Shiny, needle-like uric-acid crystals are best viewed with a polarizing microscope. The diagnosis of gout can also be made by finding these urate crystals from material aspirated from tophi nodules and bursitis fluid.
Some patients with a classic history and symptoms of gout can be successfully treated and presumed to have gout without undergoing arthrocentesis. However, establishing a firm diagnosis is still preferable since other conditions can mimic gout. These include another crystal-induced arthritis called pseudogout, psoriatic arthritis, rheumatoid arthritis, and even infection.
Tests to help diagnose gout may include :
- Joint fluid test. Your doctor may use a needle to draw fluid from your affected joint. When examined under the microscope, your joint fluid may reveal urate crystals.
- Blood test. Your doctor may recommend a blood test to measure the uric acid level in your blood. Blood test results can be misleading, though. Some people have high uric acid levels, but never experience gout. And some people have signs and symptoms of gout, but don't have unusual levels of uric acid in their blood.
- Fluid may be removed from your swollen joint with a needle. This usually causes no more discomfort than a blood test. If urate crystals can be seen in the fluid under a microscope, you have gout. If calcium crystals are seen, you have a similar condition called pseudogout.
- X-rays can sometimes be helpful, and may show tophi-crystal deposits and bone damage as a result of repeated inflammations. X-rays can also be helpful for monitoring the effects of chronic gout on the joints.
If you think you have gout, see your GP. He or she will ask about your symptoms and examine you. He or she may also ask you about your medical history.
Your GP may do one or all of the following tests or refer you to a rheumatologist (a doctor specialising in conditions that affect the joints) for them.
In diagnosing gout, the foot and ankle surgeon will take your personal and family history and examine the affected joint. Laboratory tests and x-rays are sometimes ordered to determine if the inflammation is caused by something other than gout.
Examination of joint fluid Synovial fluid can be taken from a joint through a needle. It is then examined under a microscope, where any crystals of urate can be clearly seen. Gout is the only condition in which urate crystals can be found in the synovial fluid, so this test may clinch the diagnosis if there is doubt for example where gout mimics another type of rheumatic disease such as rheumatoid arthritis. However it is more difficult, and more painful for the patient, to obtain fluid from a small joint, so unfortunately this test may not be practical in many cases of suspected gout, for example where the big toe joint is affected.
Because it is not always possible to confirm gout using these tests, the diagnosis may be based simply on the symptoms you describe together with an examination of the affected joints.
